Method of transmitting feedback information for precoding and precoding method

Abstract

Precoding methods and method for performing precoding and methods of transmitting feedback information for precoding or transmitting a signal using a multi-codebook and method of transceiving precoding information in a multi-antenna system, where a signal transmitting method in a multi-antenna system, and more particularly, a method of transceiving precoding matrix information for a multi-input multi-output (MIMO) system is disclosed. The present invention proposes a method of performing communications using an expanded unitary matrix generated from shifting a phase of a base unitary matrix. The present invention is applicable to single user MIMO, multi-user MIMO, beam forming, etc.

What is claimed is: 
     
       1. A precoding method in a transmitting end of a MIMO (Multiple Input Multiple Output) system, the precoding method comprising:
 receiving feedback information for deciding a precoding matrix comprised using at least one of a base matrix and an expansion matrix generated by performing a phase shift on the base matrix; 
 performing the precoding using the precoding matrix decided according to the received feedback information; and 
 transmitting data precoded by the precoding matrix, 
 wherein the base matrix is selected one of a DFT (discrete Fourier Transform) matrix and an antenna selection matrix considering a spatial channel correlation, and 
 wherein the base matrix is the DFT matrix when the spatial channel correlation is greater than a reference correlation, and the base matrix is the antenna selection matrix when the spatial channel correlation is less than or equal to the reference correlation. 
 
     
     
       2. The precoding method of  claim 1 , wherein the phase shift is carried out in a manner that an antenna beam pattern of the expansion matrix is phase shifted by an angle corresponding to an identical phase shift angle (Φ, Φ≧0) in comparison with a virtual beam pattern of the base matrix. 
     
     
       3. The precoding method of  claim 1 , the precoding performing step comprising the steps of:
 deciding the precoding matrix corresponding to the feedback information in a codebook including the precoding matrix information amounting to the number corresponding to a bit number of the feedback information; and 
 performing the precoding using the decided precoding matrix. 
 
     
     
       4. The precoding method of  claim 3 , wherein the codebook includes a first sub-codebook including precoding vectors derived from the DFT matrix and a second sub-codebook including precoding vectors derived from the antenna selection matrix. 
     
     
       5. The method of  claim 4 , further comprising:
 transmitting information indicating a ratio between the first sub-codebook and the second sub-codebook. 
 
     
     
       6. The precoding method of  claim 3 , wherein the codebook includes the precoding matrix adaptively decided according to a variation of the number of transmitting streams. 
     
     
       7. The precoding method of  claim 3 , wherein the precoding matrix is added in a manner that the bit number of the feedback information is incremented and wherein the added precoding matrix comprised using at least one or more expansion matrixes with a different phase shift angle (Φ, Φ≧0) from each other. 
     
     
       8. The precoding method of  claim 1 , wherein the antenna selection matrix is configured in a manner of expanding the precoding matrix for transmitting antennas less than transmitting antennas included in the system. 
     
     
       9. The precoding method of  claim 1 , wherein a result of the precoding performing step corresponds to at least one data stream for at least one user. 
     
     
       10. The method of  claim 1 , wherein the expansion matrix is determined by a product of the base matrix and a phase diagonal matrix having an exponential coefficient value incremented linearly according to an index of a transmitting antenna. 
     
     
       11. A method for precoding in a receiving end of an MIMO (Multiple Input Multiple Output) system, the method comprising:
 transmitting feedback information for deciding a precoding matrix comprised using at least one of a base matrix and an expansion matrix generated by performing a phase shift on the base matrix; and 
 receiving a signal which is precoded by the precoding matrix decided according to the feedback information, 
 wherein the base matrix is selected one of a DFT (discrete Fourier Transform) matrix and an antenna selection matrix considering a spatial channel correlation, and 
 wherein the base matrix is the DFT matrix when the spatial channel correlation is greater than a reference correlation, and the base matrix is the antenna selection matrix when the spatial channel correlation is less than or equal to the reference correlation. 
 
     
     
       12. The method of  claim 11 , wherein the phase shift is carried out in a manner that an antenna beam pattern of the expansion matrix is phase shifted by an angle corresponding to an identical phase shift angle (Φ, Φ>=0) in comparison with a virtual beam pattern of the base matrix. 
     
     
       13. The method of  claim 11 , wherein the signal is precoded by the precoding matrix corresponding to the feedback information in a codebook including the precoding matrix information amounting to the number corresponding to a bit number of the feedback information. 
     
     
       14. The method of  claim 13 , wherein the codebook includes a first sub-codebook including precoding vectors derived from the DFT matrix and a second sub-codebook including precoding vectors derived from the antenna selection matrix. 
     
     
       15. The method of  claim 14 , further comprising:
 receiving information indicating a ratio between the first sub-codebook and the second sub-codebook. 
 
     
     
       16. The method of  claim 13 , wherein the codebook includes the precoding matrix adaptively decided according to a variation of the number of transmitting streams. 
     
     
       17. The method of  claim 13 , wherein the precoding matrix is added in a manner that the bit number of the feedback information is incremented and wherein the added precoding matrix comprised using at least one or more expansion matrixes with a different phase shift angle (Φ, Φ>0) from each other. 
     
     
       18. The method of  claim 11 , wherein the antenna selection matrix is configured in a manner of expanding the precoding matrix for transmitting antennas less than transmitting antennas included in the system. 
     
     
       19. The method of  claim 11 , wherein the expansion matrix is determined by a product of the base matrix and a phase diagonal matrix having an exponential coefficient value incremented linearly according to an index of a transmitting antenna.